The present invention relates to a driver IC operable to alternately generate a display drive period and a non-display drive period to drive a display panel, and a technique useful in application to e.g. drive control of a panel module having a touch panel incorporated in a display panel.
Driver ICs operable to drive a display panel include a driver IC having a data RAM for display which is capable of temporarily holding one frame of image data. In the case of displaying a still image, successive transmission of the image data by a host processor can be stopped by displaying the image while reading out one frame of image data already accumulated in a data RAM and thus, both the power consumed by a display panel and the load to the host processor required for transmission of the image data can be reduced actually.
If such arrangement does not need to be made at all, it is not required to have a data RAM which would occupy a large area in a driver IC.
Further, in case that any attempt is made to reduce the load to a host processor while the chip footprint of a data RAM is reduced, a driver IC having a data RAM (partial RAM) for display having only several display lines of memory capacity smaller than one frame may be arranged so that it always uses a host processor to transmit display data for image data of a display region with a high update frequency, whereas for image data of a display region with a low update frequency, it causes the host processor to perform the display thereof while reading out data in a partial RAM. The arrangement like this allows the reduction in the amount of data transmission by the host processor for displaying portions of a low display update frequency, such as receive condition and status fields in a portable telephone or the like.
Considering the fact that a panel module having a display panel and a touch panel incorporated in the display panel is used frequently, it is preferable to perform the touch detection in a period during which the display driving remains stopped. This is because action noise caused at the time of display driving worsens the touch detection accuracy.
For instance, in the Japanese Unexamined Patent Publication No. JP-A-2012-59265 in view of this, the driver IC is arranged to have a data RAM with a capacity as large as one frame, intermittently display an image in blocks composed of several lines, and perform a touch sensing action in a period during which a display-drive output from the drive circuit remains stopped, whereby a high touch detection accuracy is achieved. In order to drive a display panel in blocks according to a time-sharing method like this, image data are stored, in blocks, in a data RAM with a capacity as large as one frame.